diff --git a/ApiCore-Backend/src/apiaries/apiaries.service.spec.ts b/ApiCore-Backend/src/apiaries/apiaries.service.spec.ts
index 9467667..5afa1a8 100644
--- a/ApiCore-Backend/src/apiaries/apiaries.service.spec.ts
+++ b/ApiCore-Backend/src/apiaries/apiaries.service.spec.ts
@@ -12,6 +12,7 @@ describe('ApiariesService', () => {
       create: jest.Mock;
       update: jest.Mock;
     };
+    colony: { count: jest.Mock };
   };
   let auditLog: { record: jest.Mock };
 
@@ -30,6 +31,7 @@ describe('ApiariesService', () => {
         create: jest.fn(),
         update: jest.fn(),
       },
+      colony: { count: jest.fn().mockResolvedValue(0) },
     };
     auditLog = { record: jest.fn().mockResolvedValue(undefined) };
     service = new ApiariesService(
@@ -76,6 +78,16 @@ describe('ApiariesService', () => {
     );
   });
 
+  it('deactivate throws ConflictException when active colonies remain', async () => {
+    prisma.apiary.findUnique.mockResolvedValue(existingApiary);
+    prisma.colony.count.mockResolvedValue(2);
+
+    await expect(
+      service.deactivate('apiary-1', 'user-1'),
+    ).rejects.toBeInstanceOf(ConflictException);
+    expect(prisma.apiary.update).not.toHaveBeenCalled();
+  });
+
   it('reactivate throws ConflictException when already active', async () => {
     prisma.apiary.findUnique.mockResolvedValue(existingApiary);
     await expect(
diff --git a/ApiCore-Backend/src/apiaries/apiaries.service.ts b/ApiCore-Backend/src/apiaries/apiaries.service.ts
index 8a957fa..cdd4300 100644
--- a/ApiCore-Backend/src/apiaries/apiaries.service.ts
+++ b/ApiCore-Backend/src/apiaries/apiaries.service.ts
@@ -76,6 +76,19 @@ export class ApiariesService {
 
   async deactivate(id: string, actingUserId: string): Promise<Apiary> {
     const before = await this.findById(id);
+    // Colony.apiaryId is a plain FK, not enforced against apiary status -
+    // without this guard a colony can silently keep pointing at an
+    // inactive apiary (still shows ACTIVE, still countable, but its
+    // "location" has vanished from the active apiary list). Move the
+    // colonies elsewhere or dissolve them first instead.
+    const activeColonyCount = await this.prisma.colony.count({
+      where: { apiaryId: id, status: 'ACTIVE' },
+    });
+    if (activeColonyCount > 0) {
+      throw new ConflictException(
+        `Apiary ${id} still has ${activeColonyCount} active colonies - move or dissolve them first`,
+      );
+    }
     const apiary = await this.prisma.apiary.update({
       where: { id },
       data: { status: 'INACTIVE', deactivatedAt: new Date() },